Method for operating a wind energy plant and wind energy plant

ABSTRACT

A method for operating a wind energy plant having a rotor with at least one rotor blade which has an adjustable pitch angle and a generator coupled to the rotor, and a regulation means which, if a there is a deviation of the rotation speed of the generator or rotor from a rotation speed set point, adjusts the pitch angle of the at least one rotor blade such that the rotation speed set point is reached again, wherein an electrical quantity provided by the wind energy plant by means of a generator and fed into a grid is reduced to a predetermined value in a short time by a reduction of a preset value for the generator, wherein prior to the regulation means noticing a deviation of the rotation speed of the rotor or generator from the rotation speed set point effected by the reduction of the preset value, an adjustment of the at least one rotor blade to a new pitch angle is initiated, wherein at the new pitch angle the rotation speed of the rotor or the generator reaches the rotation speed set point at the reduced electrical quantity and the current wind speed.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.This application is a reissue of U.S. Pat. No. 7,714,458,filed Apr. 16, 2008, the entire contents of which are herebyincorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

The invention relates to a method for operating a wind energy plant andto a wind energy plant having a rotor with at least one rotor bladewhich has an adjustable pitch angle, a generator coupled to the rotor,and a regulation means which, if there is a deviation of the rotationspeed of the generator or rotor from a rotation speed set point, adjuststhe pitch angle of the at least one rotor blade such that the rotationspeed set point is reached again.

Fault of a grid which is fed by the wind energy plant may cause a suddenload shedding, wherein the generator torque or the generator power ofthe wind energy plant falls off to zero within a very short time period.Moreover, it is also possible to reduce an electrical quantity providedby the plant by means of a generator and fed into a grid to apredetermined value in a controlled manner and in a short time byreduction of a preset value for the generator, such as a presetgenerator torque or the preset generator power, respectively, forexample by means of a corresponding control means of the plant. In thiscontext, in a short time means a time period of less than one minute, inparticular less than half a minute.

With increasing importance of regenerative energy sources, energy supplycompanies more and more make the same technical demands on wind energyplants or wind parks, respectively, as they do on conventional powerplants. An example is the demand for a contribution of wind energyplants to a fast reduction of excess power in the grid. To this end, theenergy supply company sends a respective signal predetermining a definedpower level. Such a signal can be independent of other preset values,for example active power set points. The energy supply companies moreand more demand a very fast reduction of the electrical energy of theplant fed into the grid. In a couple of countries, time periods of a fewseconds, for example five seconds, are discussed or already required fora reduction of load to a value of for example 20% of the capacity of thegrid connection.

In order to meet these rigorous timing requirements, the electricalquantity provided must be reduced by means of a very fast reduction ofthe generator torque or generator power, respectively. Through thisreduction of the counter load generated by the generator, however, therotor of the wind energy plant is accelerated and rotation speeds occurwhich cause the regulation means to interact by increasing the pitchangle. The pitch angle is a constructive quantity, namely the anglebetween the rotor plane and the chord line of the rotor blade. As soonas the regulation means notices a deviation of the rotation speed of therotor or generator from the rotation speed set point, it reacts bychanging the pitch angle. However, the regulation means is designed withregard to the usual wind turbulences. With regard to a sudden loadshedding, the regulation means reacts too slowly. This can lead todetrimental excess rotation speeds of the rotor or the generator,respectively. To avoid this, the generator torque or the generatorpower, respectively, can only be reduced with a limited speed. For thisreason, it is difficult to fulfill the strict requirements of the energysupply companies with current systems.

In particular for wind parks, an additional problem is that the requestfor a reduction of the overall active power provided must be allocatedto the individual wind energy plants in an intelligent manner.Receiving, evaluating and transmitting the individual set point signalsto the plants by means of the wind park controller takes a certain time,which is then no longer available for a reduction of the load by theplants. The aforementioned problem is therefore getting worse for plantsin wind parks.

With known systems, it is not possible to change the active power of awind energy plant to 20% of the rated power within a few seconds, forexample within five seconds. In the alternative, the electrical quantityprovided can be reduced by disconnecting the plant from the grid, thatis, by a shutdown, but this is often undesirable. In particular, ashutdown of the plant is acceptable only under certain exceptionalconditions.

Based on the prior art described, the invention was therefore based onthe problem to provide a method and a wind energy plant that allow for afast load reduction to a new stable operating point withoutdisconnection from the grid.

BRIEF SUMMARY OF THE INVENTION

The problem is solved by the invention on the one hand by a method foroperating a wind energy plant, the wind energy plant having a rotor withat least one rotor blade which has an adjustable pitch angle, the windenergy plant having a generator coupled to the rotor, and a regulationmeans which, if there is a deviation of the rotation speed of thegenerator or rotor from a rotation speed set point, adjusts the pitchangle of the at least one rotor blade such that the rotation speed setpoint is reached again, wherein an electrical quantity provided by thewind energy plant by means of a generator and fed into a grid is reducedto a predetermined value in a short time by reduction of a preset valuefor the generator, and wherein prior to the regulation means noticing adeviation of the rotation speed of the rotor or generator from therotation speed set point effected by the reduction of the preset value,an adjustment of the at least one rotor blade to a new pitch angle isinitiated, wherein at the new pitch angle the rotation speed of therotor or generator reaches the rotation speed set point at the reducedelectrical quantity and the current wind speed, that is at the windspeed acting on the rotor.

On the other hand, according to the invention, the problem is solved bya wind energy plant having a rotor with at least one rotor blade whichhas an adjustable pitch angle, the wind energy plant having a generatorcoupled to the rotor, a regulation means designed to adjust the pitchangle of the at least one rotor blade such that, if there is a deviationof the rotation speed of the generator or rotor from a rotation speedset point, the rotation speed set point is reached again, and a controlmeans designed to reduce an electrical quantity which is provided by thewind energy plant by means of a generator and fed into a grid to apredetermined value in a short time by reduction of a preset value forthe generator, wherein the control means is further designed to initiatean adjustment of the at least one rotor blade to a new pitch angle priorto the regulation means noticing a deviation of the rotation speed ofthe rotor or generator from the rotation speed set point effected by thereduction of the preset value, wherein at the new pitch angle therotation speed of the rotor or generator reaches the rotation speed setpoint at the reduced electrical quantity and the current wind speed.Therein, the deviation of the rotation speed of the rotor or generatorfrom the rotation speed set point noticed by the regulation means is adeviation large enough to trigger a regulation action. The rotationspeed set point can be the nominal rotation speed of the generator orthe rotor, respectively. The preset value is a value given to thegenerator in order to obtain a desired electrical quantity actuallyprovided by the plant, such as for example active power.

Given a signal to quickly reduce the load, a reduction of the presetvalue, for example the generator torque or the generator power, andtherewith of the electrical quantity, is performed as quickly aspossible. In order to avoid that a dangerous excess rotation speed ofthe rotor or generator, respectively, can occur, according to theinvention, an adjustment to a new, larger pitch angle is initiated atthe same or at an earlier point in time. That is, the pitch angle isincreased anticipatory in order to reduce the received power of therotor, so that an undesirable increase of the rotation speed as a resultof the reduced preset value is avoided. According to the invention, thecontrol element for reducing the electrical quantity and the controlelement for the pitch angle cooperate. The wind energy plant staysconnected to the grid during the fast load reduction. A disconnectionfrom the grid does not take place.

The electrical quantity can be reduced to a value of zero or to a valuedifferent from zero. The new pitch angle to be set can be determinedbased on the predetermined value for the electrical quantity, thecurrent rotation speed of the rotor or generator, respectively, thecurrent pitch angle and the operating condition of the plant. This isespecially advantageous when reducing the electrical quantity to a valuenot equal to zero.

The wind energy plant can have a suitable measurement device formeasuring the wind speed. The regulation used in the wind energy plantcan for example work with two controllers coupled to each other, namelya converter controller and a pitch controller. The aim of the overallsystem is to accomplish an optimal power output of the plant to the gridin regular operating mode. When the wind speed reaches the nominal windspeed, from this time on the active power output is to be regulated orlimited, respectively, to the nominal power. In this case, the plantscan for example work as so-called speed-controlled plants, wherein abovethe nominal wind speed and when the rated power is reached, the rotationspeed of the plant is kept constant. The two controllers of the plantare working together conditionally, that is through the rated power andspecial plant-system-states (for example connecting to the grid,hysteresis), the cooperation of the controllers is well-defined.

The invention relates to special operating states the controller of theplant is not designed for, and achieves a safety increase of the plantby acting on the pitch adjustment. In particular, according to theinvention, it is possible to reduce load to a stable power value in ashort period of time, for example less than a minute, especially lessthan half a minute, preferably not exceeding 10 seconds, in particularnot exceeding 5 seconds or less than 5 seconds. The predetermined valueof the reduced electrical quantity can be for example 60%, preferably40%, more preferably 20% of the nominal value of the electricalquantity. Thenceforward until cancelled, the set point for theelectrical quantity stays at the predetermined reduced value. The methodof the invention and the plant control means of the invention,respectively, can be used advantageously also for a fast increase of theelectrical quantity provided by the plant, when for example the pitchangle is reduced anticipatory in order to increase the received power ofthe plant quickly.

It is possible to perform the adjustment of the new pitch angle by theregulation means. In this case, the control means only initiates theadjustment of the new pitch angle. So, the regulation can remain activeduring the activation of the new pitch angle. The control means and theregulation means can form a combined device. It is possible to determinethe new pitch angle for the predetermined value of the reducedelectrical quantity. To this end, the control means of the plant can bedesigned correspondingly. In order to determine this new pitch angle,the control means can be provided for example with characteristicdiagrams and/or functions.

The rotor of the wind energy plant usually has more than one rotorblade, for example three rotor blades. Then, correspondingly, the pitchangles of all rotor blades can be adjusted according to the invention.Also, the wind energy plant can be part of a wind park, wherein theplants of the wind park are controlled by a wind park controller.

The wind energy plant of the invention can be suitable for performingthe method according to the invention.

With regard to practice, it is especially feasible if the preset valueis the preset generator torque or the preset generator power. Accordingto a further especially feasible aspect, the electrical quantity can bethe active power actually provided by the wind energy plant. Accordingto another aspect, the adjustment of the new pitch angle can beperformed by reducing by a defined offset a rotation speed set pointsupplied to the regulation means. The pitch controller establishes thedifference between a rotation speed set point supplied to the pitchcontroller and a current rotation speed supplied to the pitch controllerfor example by a measurement device. In so far as a deviation isdetected, the pitch angle is changed by the controller. By subtractingan offset signal from the rotation speed set point supplied to thecontroller, within the controller a large set point/current valuedifference can be generated very quickly, leading to a correspondinglyfast regulation action by the controller. For the adjustment of the newpitch angle, a switching on of a disturbance variable is performed in anespecially simple manner. According to an alternative or additionalapproach to the adjustment of the new pitch angle, a rotation speed setpoint supplied to the regulation means can be increased by a definedoffset. Furthermore, a minimal and a maximal pitch angle are usuallygiven to the regulation means, limiting the adjusting range of thecontroller. In this way, the controller can determine pitch angles onlywithin the limits formed by the minimal and maximal angles. The maximumpitch angle usually is about 90° for all operating states, that is flagposition of the rotor blade. The minimal pitch angle depends on theoperating state of the plant. In regular production mode, it is usually0°. An alternative or additional option for adjusting the new pitchangle therefore is to increase the minimal pitch angle supplied to theregulation means by a defined offset. With this design as well, aregulation action can be initiated quickly and in an especially simplemanner.

By adding a defined offset, that is a defined value, to an inputvariable of the regulation means, a fast influence on the regulationmeans is possible. Therein, the offset is defined such that the pitchangle desired in each case is adjusted quickly. For example, the offsetvalues can be determined empirically and retained in characteristicdiagrams. It is possible to add a defined offset to only one or to aplurality of input variables of the regulation means. The offset can becancelled after a certain time and/or when going below a predeterminedrotation speed of the generator or rotor. According to another aspect,the offset can be reduced over time to zero starting from an initialmaximum value. In this aspect, the regulation means is therefore putdown to its regular operating mode over time with the regular inputvariables for compensation of wind turbulences, by means of reducing theadded offset over time to zero.

This shall be illustrated on the basis of an example for adding anoffset to the input variable of the minimum pitch angle.

For determining a new, minimal pitch angle to be supplied to theregulation means, the current actual pitch angle can be increased by arespective pitch angle offset. A value A may be subtracted from the newminimal pitch angle determined in the described manner. The value A istime-variant and is increased, starting from zero, by means of atime-ramp or a function to a value equal to the pitch angle offset. Inthis way, the pitch angle offset is reduced over time, starting from aninitial maximum value, to zero. The value A can be adjusted such thatthe rotation speed does not fall below the nominal rotation speed.

The offset to be added in each case can be determined by means of atleast one characteristic diagram which can be retained in the controlmeans of the plant for this purpose. Such a characteristic diagram cancontain for example the pitch angles required to reach the rotationspeed set point for the rotation speed of the rotor or generator,respectively, in dependence on different wind speeds for differentpredetermined electrical quantities, for example active power values. Inthe alternative, it is also possible to calculate the offset by means ofat least one function which can be retained in the control means forthis purpose. Such a function can for example describe mathematicallythe pitch angle required for a rotation speed set point in dependence ondifferent wind speeds for different predetermined electrical quantities,for example active power values.

According to another aspect, it is possible to initiate the adjustmentto a new pitch angle only if the rotation speed of the rotor orgenerator is above a threshold rotation speed and/or if the presetvalue, for example the generator torque or the generator power, prior toits reduction is above a threshold preset value, that is for example athreshold generator torque or a threshold generator power. To this end,the control means can have a comparison means for comparing the rotationspeed of the rotor or generator to a threshold rotation speed or thepreset value to a threshold preset value, respectively. In particularwhen the pitch angle is for example 0°, a fast load shedding can lead toan undesired excess rotation speed only if the rotation speed of therotor or generator, respectively, is close to the nominal rotationspeed. For this reason, in such a case the adjustment to a new pitchangle is necessary only above a process- and plant-dependent thresholdrotation speed or a process- and plant-dependent threshold preset value,respectively. The threshold value can for example be the nominalrotation speed, or a certain percentage of the nominal torque or thenominal power. The threshold value can then increase with decreasingdifference between the nominal rotation speed, the nominal torque or thenominal power, respectively, and the current rotation speed, the currenttorque or the current power, respectively.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following, an embodiment of the invention is explained in greaterdetail on the basis of drawings.

FIG. 1 shows schematically a block diagram illustrating the operation ofthe wind energy plant of the invention, and

FIG. 2 shows schematically a characteristic diagram illustrating theoperation of the method of the invention and of the wind energy plant ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein a specific preferred embodiment of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiment illustrated

In FIG. 1, a block diagram is shown illustrating the operation of thewind energy plant of the invention. The wind energy plant has, in amanner known as such, a power train not shown in detail which carries atits front end a rotor also not shown having at least one, preferablythree rotor blades not shown, and which leads to a so-called generatorconverter unit at is rear end. The generator converter unit has agenerator not shown, a converter 10 and a converter controller 11controlling the converter 10 through a control channel 9. By means ofthe converter controller 11, the active power actually provided by theplant is adjustable. The generator converter unit is not necessarilydesigned as a constructive or structural unit, but denominates generatorand converter working together in order to provide the desiredelectrical quantity of the wind energy plant, for example the activepower. The converter controller 11 receives as input variables an activepower set point P_(S) and a current generator rotation speed n_(GI), asillustrated by channels 7, 8.

The pitch angle of the rotor blade or the rotor blades, respectively, isadjustable by a regulation means 12, in the present example a pitchcontroller 12 (also: blade controller), and a pitch angle control means14 (also: pitch activation). The rotation speed of the generator orrotor, respectively, can be controlled through the blade angle, so thatthe pitch controller 12 works as a rotation speed controller 12. Thepitch controller 12 is supplied with a generator rotation speed setpoint n_(GS) through channel 13 and with the current generator rotationspeed n_(GI) through a channel 15 as input variables for the regulation,as illustrated in FIG. 1 by node 16. In addition, the pitch controller12 receives a maximal and a minimal pitch angle which limit the validadjustment range for the pitch angle. Corresponding to the inputvariables, the pitch controller 12 controls the pitch angle controlmeans 14 through the channel 18.

If a fast reduction of an electrical quantity fed into an electric grid,for example the active power, is requested, the signal (1) for the fastreduction is applied to a control means 22 with an evaluation programthrough channels 24 and 26, or, as the case may be, through a delay 20through channels 24 and 28, respectively. The control means 22 controlsthe converter controller 11 directly through channel 30 in order toinitiate the desired reduction of the electrical quantity. In order toprevent a related increase of the rotation speed of the generator orrotor, the control means 22 can generate an offset (2) for the minimalpitch angle, an offset (3) for the generator rotation speed set pointn_(GS) and/or an offset (4) for the current generator rotation speedn_(GI) at the same point in time or earlier as the reduction of theelectrical quantity is initiated, prior to the pitch controller 12notices a deviation of the rotation speed of the rotor or generator froma rotation speed set point.

The offset (2) for the minimal pitch angle can be supplied directly tothe pitch controller 12, as shown by channel 32. This offset (2) for theminimal pitch angle can be selected such that the new minimal pitchangle is in each case higher than the current pitch angle applied.Likewise, the offset (3) for the generator rotation speed set pointn_(GS) can be added to the generator rotation speed set point n_(GS), asshown by channel 34. In particular, the offset (3) can be negative, sothat the rotation speed set point supplied to the pitch controller 12 isreduced by the offset (3). Subsequently, the generator rotation speedset point modified by the offset (3) is supplied to the pitch controller12. Finally, the offset (4) for the current generator rotation speedn_(GI) can be added to the current generator rotation speed n_(GI), asillustrated by channel 36. The current generator rotation speed n_(GI),increased by the offset (4) being positive in particular, is thensupplied to the pitch controller 12 through channel 15 and node 16.

Generating and supplying the offsets (2), (3) and/or (4) to the pitchcontroller 12 in each case leads to the pitch controller 12 controllingthe pitch angle control means 14 such that the pitch angle control meansincreases the pitch angle of the rotor blades in order to reduce therotation speed of the generator or rotor, respectively. In this way, bymeans of the fast power reduction, detrimental excess rotation speeds ofthe generator or rotor, respectively, caused under certaincircumstances, are avoided in advance. The offsets (2), (3) and (4) canbe generated and supplied to the pitch controller 12 alternatively or inany combination. The size of the offsets (2), (3), and (4) is selectedby the control means 22 such that the rotation speed of the rotor orgenerator at the power reduction needed in each case, as a consequenceof the effected adjustment to a new pitch angle, again adopts therotation speed set point.

The determination of the new pitch angle needed in each case shall beexplained on the basis of the diagram shown in FIG. 2. In thecharacteristic diagram shown in FIG. 2, the current wind speed in [m/s]acting on the wind energy plant is assigned to the x-axis. The pitchangle ν in [°] of the rotor blades of the wind energy plant, in thepresent example of all three rotor blades, is assigned to the y-axis.Five characteristic curves for different electrical power values P1, P2,P3, P4, P5 provided to a grid by a generator are found in the diagram,wherein P1>P2>P3>P4>P5. The characteristic curves in each case indicatethe values leading to the rotation speed set point for the generator orrotor desired in each case.

With the characteristic diagram, it is possible to determine a targetpitch angle at which the rotation speed of the rotor or generator againadopts the rotation speed set point on the basis of the current plantpower and the requested reduced target power of the plant at a currentwind speed. This shall be explained by means of an example:

At the working point denoted in the figure by A, the wind energy plantgenerates an active power P3 at a wind speed of about 11 m/s and at apitch angle of about 3°. If now an energy supply company requests apower reduction for example to a lower power P5, the correspondingworking point of the wind energy plant can be determined by means of thecharacteristic diagram. In the diagram, it is denoted by B. Thus, it isswitched from the characteristic curve for P3 to the characteristiccurve for P5. Given the wind speed staying constant, at the reducedpower P5 it is necessary to increase the pitch angle to about 12° inorder to again establish the preconditions for reaching the rotationspeed set point of the rotor or generator, respectively. For other windspeeds, the needed pitch angle can be determined along thecharacteristic curve. Thus, for a predetermined power, in each case aregulation is performed along the corresponding characteristic curve.

In order to avoid detrimental excess rotation speeds in the course ofthe fast load reduction by a fast reduction of the preset value, forexample the generator torque or the generator power, according to theinvention, already at the point in time when the reduction of the presetvalue is initiated, or even earlier, the adjustment of the three rotorblades to the new pitch angle of about 12° is initiated. This is donefor example by increasing the minimal pitch angle supplied to theregulation means 12 by an offset, as explained above. In the exampleillustrated, the new minimal pitch angle to be applied is determined byincreasing the current pitch angle of 3° by an offset of 9°. So, the newminimal pitch angle to be applied corresponds to the desired targetangle of 12°. Of course, in the alternative or in addition, it is alsopossible to add an offset to other input variables of the regulationmeans, for example the rotation speed set point or the current rotationspeed of the rotor or generator, respectively, supplied to theregulation means.

Afterwards, in order to hand over full control again to the regulationmeans 12 gradually, the offset and with it the minimal pitch anglesupplied to the regulation means 12 is reduced from the initial maximalvalue of the offset along a time-ramp or a function to zero. Then, theregulation means 12 can regularly control the pitch angle at the reducedactive power and the reduced preset value, corresponding to theoccurring wind speed variations.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the claims where the term“comprising” means “including, but not limited to”. Those familiar withthe art may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims.

Further, the particular features presented in the dependent claims canbe combined with each other in other manners within the scope of theinvention such that the invention should be recognized as alsospecifically directed to other embodiments having any other possiblecombination of the features of the dependent claims. For instance, forpurposes of claim publication, any dependent claim which follows shouldbe taken as alternatively written in a multiple dependent form from allprior claims which possess all antecedents referenced in such dependentclaim if such multiple dependent format is an accepted format within thejurisdiction (e.g. each claim depending directly from claim 1 should bealternatively taken as depending from all previous claims). Injurisdictions where multiple dependent claim formats are restricted, thefollowing dependent claims should each be also taken as alternativelywritten in each singly dependent claim format which creates a dependencyfrom a prior antecedent-possessing claim other than the specific claimlisted in such dependent claim below.

This completes the description of the preferred and alternateembodiments of the invention. Those skilled in the art may recognizeother equivalents to the specific embodiment described herein whichequivalents are intended to be encompassed by the claims attachedhereto.

What is claimed is:
 1. Method for operating a wind energy plant, thewind energy plant having a rotor with at least one rotor blade which hasan adjustable pitch angle, the wind energy plant having a generatorcoupled to the rotor, and a regulation means which, if there is adeviation of the rotation speed of the generator or rotor from arotation speed set point, adjusts the pitch angle of the at least onerotor blade such that the rotation speed set point is reached again,wherein an electrical quantity provided by the wind energy plant bymeans of a generator and fed into a grid is reduced to a predeterminedvalue in a short time by reduction of a preset value for the generator,characterized in that prior to the regulation means (12) noticing adeviation of the rotation speed of the rotor or generator (n_(GI)) fromthe rotation speed set point (n_(GS)) effected by the reduction of thepreset value, an adjustment of the at least one rotor blade to a newpitch angle (ν) is initiated, wherein at the new pitch angle (ν) therotation speed of the rotor or generator (n_(GI)) reaches the rotationspeed set point at the reduced electrical quantity (P1, P2, P3, P4, P5)and the current wind speed (V_(Wind)).
 2. Method according to claim 1,characterized in that the preset value is a preset generator torque or apreset generator power.
 3. Method according to claim 1, characterized inthat the electrical quantity (P1, P2, P3, P4, P5) is the active power(P1, P2, P3, P4, P5) of the wind energy plant.
 4. Method according toclaim 1, characterized in that the new pitch angle (ν) is adjusted byway of reducing a rotation speed set point (n_(GS)) supplied to theregulation means (12) by a defined offset.
 5. Method according to claim4, characterized in that the offset is reduced over time to zerostarting from an initial maximum value.
 6. Method according to claim 4,characterized in that the offset is determined by means of acharacteristic diagram.
 7. Method according to claim 4, characterized inthat the offset is determined by means of at least one function. 8.Method according to claim 1, characterized in that the new pitch angle(ν) is adjusted by way of increasing a current rotation speed (n_(GI))supplied to the regulation means (12) by a defined offset.
 9. Methodaccording to claim 1, characterized in that the new pitch angle (ν) isadjusted by way of increasing a minimal pitch angle supplied to theregulation means (12) by a defined offset.
 10. Method according to claim1, characterized in that the adjustment to the new pitch angle (ν) isinitiated only if the rotation speed of the rotor or generator (n_(GI))is above a threshold rotation speed and/or if the preset value prior toits reduction is above a threshold preset value.
 11. Wind energy planthaving a rotor with at least one rotor blade which has an adjustablepitch angle, the wind energy plant having a generator coupled to therotor, a regulation means designed to adjust the pitch angle of the atleast one rotor blade such that, if there is a deviation of the rotationspeed of the generator or rotor from a rotation speed set point, therotation speed set point is reached again, and a control means designedto reduce an electrical quantity which is provided by the wind energyplant by means of a generator and fed into a grid to a predeterminedvalue in a short time by reduction of a preset value for the generator,characterized in that the control means (22) is designed to initiate anadjustment of the at least one rotor blade to a new pitch angle (ν)prior to the regulation means (12) noticing a deviation of the rotationspeed of the rotor or generator (n_(GI)) from the rotation speed setpoint (n_(GS)) effected by the reduction of the preset value, wherein atthe new pitch angle (ν) the rotation speed of the rotor or generator(n_(GI)) reaches the rotation speed set point (n_(GS)) at the reducedelectrical quantity (P1, P2, P3, P4, P5) and the current wind speed(V_(Wind)).
 12. Wind energy plant according to claim 11, characterizedin that the preset value is a preset generator torque or a presetgenerator power.
 13. Wind energy plant according to claim 11,characterized in that the electrical quantity (P1, P2, P3, P4, P5) isthe active power (P1, P2, P3, P4, P5) of the wind energy plant.
 14. Windenergy plant according to claim 11, characterized in that the controlmeans (22) is designed to adjust the new pitch angle (ν) by way ofreducing a rotation speed set point (n_(GS)) supplied to the regulationmeans (12) by a defined offset.
 15. Wind energy plant according to claim14, characterized in that a characteristic diagram for determining theoffset is retained in the control means (22).
 16. Wind energy plantaccording to claim 14, characterized in that at least one function forcalculating the offset is retained in the control means (22).
 17. Windenergy plant according to claim 11, characterized in that the controlmeans (22) is designed to adjust the new pitch angle (ν) by way ofincreasing a current rotation speed (n_(GI)) supplied to the regulationmeans (12) by a defined offset.
 18. Wind energy plant according to claim11, characterized in that the control means (22) is designed to adjustthe new pitch angle (ν) by way of increasing a minimal pitch anglesupplied to the regulation means (12) by a defined offset.
 19. Windenergy plant according to claim 11, characterized in that the controlmeans (22) is designed to reduce the offset over time to zero startingfrom an initial maximum value.
 20. Wind energy plant according to claim11, characterized in that the control means (22) has a comparison meansfor comparing the rotation speed of the rotor or generator (n_(GI)) to athreshold rotation speed and in that the control means (22) is designedto initiate the adjustment to the new pitch angle (ν) only if therotation speed of the rotor or generator (n_(GI)) is above a thresholdrotation speed and/or if the preset value prior to its reduction isabove a threshold preset value.
 21. A method for operating a wind energyplant, the wind energy plant having a rotor with at least one rotorblade which has an adjustable pitch angle, the wind energy plant havinga generator coupled to the rotor, and a regulation means for adjustingthe pitch angle of the at least one rotor blade, the wind energy plantproviding an electrical quantity to a grid, the method comprising:reducing the electrical quantity to a reduced electrical quantity in ashort time period, adjusting the at least one rotor blade to a new pitchangle (ν) when a reduction to the reduced electrical quantity isinitiated, wherein a rotation speed of the rotor or generator (n_(GI))at the new pitch angle (ν) reaches a rotation speed set point of therotor or generator (n_(GS)) at the reduced electrical quantity andcurrent wind speed (V_(Wind)), wherein the rotation speed set point isat least equal to a nominal rotation speed of the generator or rotor.22. The wind energy plant of claim 21, wherein the short time period isless than a minute.
 23. The method according to claim 21, characterizedin that the electrical quantity is an active power (P1, P2, P3, P4, P5)of the wind energy plant.
 24. A wind energy plant configured to feed anelectrical quantity into an electric grid, the wind energy plantcomprising: a rotor with at least one rotor blade with an adjustablepitch angle; a generator coupled to the rotor; a regulation means foradjusting the pitch angle of the at least one rotor blade; a controlmeans, the control means configured to reduce the electrical quantity toa reduced electrical quantity in a short time period and to adjust theat least one rotor blade to a new pitch angle (ν) when the reduction ofthe electrical quantity to the reduced electrical quantity is initiated,wherein a rotation speed of the rotor or generator (n_(GI)) at the newpitch angle (ν) reaches a rotation speed set point of the rotor orgenerator (n_(GS)) at the reduced electrical quantity and current windspeed (V_(Wind)).
 25. The wind energy plant of claim 24, wherein theshort time period is less than a minute.
 26. The method according toclaim 24, characterized in that the electrical quantity is an activepower (P1, P2, P3, P4, P5) of the wind energy plant.